Virus concerns wine grape growers

Expansion of Washington's wine grape acreage and tonnage may be driving a new virus from propagation of unclean plants.

KENNEWICK, Wash. — Washington’s wine grape industry continues expanding in acreage and tonnage, but there is concern about a relatively new disease — the Grapevine red blotch.

The red blotch virus probably has been active for years but wasn’t known because it was mistaken for another disease known as leaf roll, said Richard Hoff, a viticulturist for Horse Heaven Hill vineyards of Ste. Michelle Wine Estates, Woodinville.

Symptoms are similar to leaf roll — red leaves and grapes that are low in sugar and color and high in acid, he said.

Grapevine red blotch has only been known the past three years and there is no cure, Hoff said. The only remedy is yanking infected vines, and some growers have removed whole blocks of vineyard, he said.

There is no known insect vector so the source is believed to be propagation of unclean plant material coinciding with growth of industry acreage.

“It definitely is a serious problem. Right now there’s no commercial testing lab in Washington which is a little bit of an issue because growers have to go to California for testing,” Hoff said.

But most growers don’t do that because it’s too expensive at up to $200 per sample, he said.

Large estate companies, like Ste. Michelle, take care to flag and not use infected grapes, but smaller growers often can’t afford that loss or crush grapes not knowing they have the disease, he said.

Naidu Rayapati, a virologist at Washington State University’s Irrigated Agriculture Research and Extension Center, Prosser, does limited sampling for growers, is trying to determine how widespread red blotch is and how much it affects wine, Hoff said.

“He thinks leaf hopper spreads it but other labs haven’t confirmed that so it’s anecdotal,” he said.

Hoff and Rayapati were to lead a session on red blotch and leaf roll at the last day of the annual meeting of the Washington Association of Wine Grape Growers in Kennewick, Feb. 7.

During the first day, Feb. 5, Steve Warner, president of the Washington State Wine Commission, said 209,000 tons of wine grapes were produced in Washington in 2013, up from 188,000 tons the year before. He said he does not foresee any leveling soon.

There was discussion of the history and future of Chardonnay, first planted in the state 50 years ago and the most prominent variety.

The 2013 season clocked in very close to 2003 in heat units, 2,843 compared with 2,828, said Wade Wolfe, owner and winemaker at Thurston Wolfe Winery, Prosser. But too much of the 2013 heat came too early and was wasted in terms of benefiting the crop, Wolfe said in his annual crop review. Heat was flat late in the season and sugar levels didn’t rise much, he said.

May and June were the wettest months and there was some localized hail damage, he said. Wildfire smoke wasn’t as severe as in 2012 and apparently did not affect aroma and flavor, he said.